1. Field of the Invention
The present disclosure relates to a method of plasma etching.
2. Description of the Related Art
Conventionally, as a technology that realizes finer microfabrication of semiconductor devices, a method using self-aligned vias (SAV) has been disclosed (see, for example, the United States Laid-open Patent Publication No. 2015/0206792). In a method using SAV, plasma etching is executed using as a mask a hard mask that is formed of an organic film such as resist, and a metal-containing film such as titanium nitride (TiN), for example, to form holes into a low-k film that is used as a film between wiring layers. Note that a low-k film is a generic term of films that have the relative permittivity lower than that of SiO2.
However, in a method as described above, the selectivity of the metal-containing film with respect to the low-k film is not sufficient in plasma etching. Therefore, if plasma etching is executed with the organic film and the metal-containing film as the mask, there may be a case where so-called “encroachment” is generated, namely, a part of the metal-containing film is encroached.